Problem: $\dfrac{4}{100} + \dfrac{8}{10} = {?}$
Solution: The fractions must have the same denominator before you can add them. Rewrite $\dfrac{8}{10}$ as $\dfrac{80}{100}$ $\dfrac{4}{100} + \dfrac{80}{100} = {?}$ $ = \dfrac{84}{100}$